Zinc coating method and apparatus therefor



Sept. 5, 1961 A. BEHL 2,998,647

ZINC COATING METHOD AND APPARATUS THEREFOR Filed April 2, 1957 3 Sheets-Sheet 1 INVENTOR. flz fi/V Eff/L BY WM? 73/ Sept. 5, 1961 A. BEHL 2,998,647

ZINC COATING METHOD AND APPARATUS THEREFOR Filed April 2, 1957 3 Sheets-Sheet 2 INVENTOR. flm/v 55/14 Sept. 5, 1961 A. BEHL ZINC COATING METHOD AND APPARATUS THEREFOR Filed April 2, 1957 3 Sheets-Sheet 3 INVENTOR.

me BEHL wm z/mgzww' United States Patent 2,998,647 ZINC COATING METHOD AND APPARATUS THEREFOR 'Alan Behl, Aurora, 11]., assignor to Rail'oc Company,

Inc., Plainfield, 111., a corporation of Dlinois Filed Apr. 2, '1957, Ser. No. 650,240 3 Claims. (Cl. 29-527) My invention relates to a method of zinc coating and to apparatus used for this purpose. 7

My invention relates more particularly to a method of zinc coating wherein the zinc is applied in the form of zinc dust that is disposed in a fluid carrier, the mixture being agitated so that the zinc dust is thoroughly intermingled in the carrier and is applied much as a coolant to metal dies or forming tools which create heat and friction while the metal forming is taking place, the suspension fluid being directed to the vicinity of the metal deformation, at which stage, due to the heat and pressure to which it is subjected, a coating or plating action takes place.

As is Well known in the art, zinc is principally used for galvanizing iron and steel. If a clean iron object is dipped into molten zinc, the zinc forms a protective coating that prevents the iron from rusting. For this purpose enormous quantities of zinc are used by the steel industry for galvanizing sheets, wires, pipes, chains, bolts and screws.

There are two generally known processes by which zinc galvanizing of iron and steel is done; one is known as the electrolytic plating process, and the other is known as the dipping process. For some uses the electrolytic process is preferred, since with this process there is less chance of the zinc flaking due to bending or other deformation of the metal that has been coated.

Iron or other metal is dipped in molten zinc to receive a coating which resists rust and weathering. In the case of silos, where cement staves, wooden and monolithic ma terials are used for the walls, hoops encircle the silo and are connected together by couplers. The ends of these rods or hoops are usually threaded to receive tightening nuts, and since they are continuously exposed to the weather, both the nuts and the threads must be weather resistant to prevent rusting.

In one process of manufacturing these rods, they are zinc coated or galvanized before shipment to the fabricator of the rods for silos, warehouses or other buildings for which they are used. At the fabricator, these rods are normally run through a threading machine of a well known type which has a stationary die and a reciprocating die which rolls a thread on the end of the red as it is being moved forward between the dies. In this operation the zinc coating that has been on the rod is damaged in that there is a certain amount of flaking oif of particles of the coating, and due to the formation of the threads, there is a thinning out of the balance of the coating to an unsafe degree. The usual zinc coating of rods of this type is .0010 of an inch, and by the stretching of the metal in its deformation to provide threads, this thickness of coating is thinned out and entire flakes drop so that a recoating of the threaded ends of the rods is made necessary.

I have found that a coating of zinc can be applied to metal during its deformation, as for example into threads or after butt or other welding or other metal deformation, by appropriate forming dies, by providing zinc dust in a suspension fluid and directing a stream of this fluid on the work piece as the deformation of metal is taking place. This is due in some degree to the fact that zinc becomes malleable and ductile between the temperatures of 120 C. and 150 C., and combines readily with hot metal surfaces to form a protective coating thereon. Thus where the zinc dust is accordingly directed in a continuous place, a zinc coating is formed upon the surface of this metal.

In the embodiment of the invention which is described herein, I have illustrated the method of coating the threaded ends of rods and have shown an apparatus for carrying out this process, it being understood, of course, that by the same process and with generally similar apparatus, many other types of metal objects may be coated, the apparatus generally being that shown herein.

For a more comprehensive understanding of the invention and one type of apparatus for carrying out the same, reference is had to the following description andv the accompanying drawings, upon which:

FIG. 1 is a schematic view showing the use of an apparatus for threading the ends of rods and zinc coating the same simultaneously;

FIG. 2 is an enlarged fragmentary view of the end of a galvanized rod before it is threaded;

FIG. 3 is a similar view of the same after it has been threaded and coated again;

FIG. 4 is a cross-sectional view through the stationary and reciprocating dies of a standard thread-rolling machine showing the zinc coated rod at the start of the thread rolling operation;

FIG. 5 is a similar cross-sectional view through the stationary and reciprocating dies of a standard thread rolling machine showing the zinc coated red at the end of the thread rolling operation; and

FIG. 6 is a transverse section through the dies taken on the line 6-6 of FIG. 4 showing how the thread forming takes place in a bath of fluid carrying zinc dust in suspension therein.

In the embodiment of the invention which I have chosen to illustrate and describe a specific apparatus for carrying out the method of zinc coating, I provide the usual thread rolling machine 10* shown indotted lines in FIG. 1, provided with the stationary thread rolling die 12 and the reciprocating die 14. As is usual in machines of this type, the rod R or other object to be threaded is inserted at the forward end between the two dies and then the die 14 is moved forward, rolling the rod R between the dies, the teeth of the dies being tapered so that towards the end of the movement the V-shaped thread has been formed in the metal.

The mechanism which I show may include a nozzle 16 which is located adjacent the forward end 18 of the stationary die 12 and below the front end 20 of the re ciprocating die 14. The nozzle '16 is at the end of a conduit 22 which extends to a pump 24 that is driven by a motor 26. The pump is in communication with a reservoir 30 by means of an inlet conduit 28, the reservoir 30 being vertically disposed and having an open upper end 32. I provide an agitator motor 34 for driving a pair of agitators 36 that are mounted upon a vertically disposed shaft 38 extending from the motor 34 downwardly into the reservoir 30.

The excess fluid. or coolant flows off the forward end of the stationary die 12 during an operation and is'dropped through a screen 40 into a funnel-shaped container 42 connected by a conduit 44 to a second pump 46. The pump 46 has an outlet conduit 48 extending from the end of the same to the upper end of the reservoir 32 whereby the coolant or suspension fluid is strained and pumped back into the reservoir after it has been used on the dies 12 and 14.

The fluid which I employ for etfecting the zinc coating of the threads during their formation may consist of zinc dust that is mixed with a suspension fluid. This fluid may be one of various types of liquids. Oil alone has been Patented Sept. 5, 1961 found a satisfactory carrier agent when the zinc dust is thoroughly mixed with the same by the agitator blades 36. Various detergents such as liquid soap and water have been found to be even a better carrying agent, one objection to a soapy mixture being, however, that a foaming action results. One of the preferred suspension fluids, I have found, is made for Railoc Company, Inc., owners of this application under the trade name R-138 which I mix in the following proportions:

7 parts suspension fluid, 3 parts water, 3 pounds of zinc dust to the gallon of above mixture.

I have also found that by heating this mixture to a temperature of about 160 F. in the reservoir 30, better results are obtainable. Accordingly I have applied a heating element H about the reservoir to effect this heating action.

The zinc coating of the thread walls during the threading of the rod is accomplished in the following manner: As the rod R is moved forward over the front end of the lower die 12, there is a continuous flow of fluid F running over the face of the die from the nozzle 16. The fluid carries the minute particles of zinc dust which cover the entire face of the die 12. As the reciprocating die 14 is moved forward to begin the deforming action of the die teeth 14:: over the die teeth 12a, the rod is continuously subjected to a wetting by the fluid. Due to the heat generated by the deformation of the metal as the grooves of the teeth are pressed into the rod and the friction that is encountered, the minute particles of zinc dust are also subject to this heat and friction and become impregnated or pressed on the surface of the deformed metal. This action continues throughout the travel of the rod forward so that when it has been completely threaded by the dies, the entire surface that has been subjected to deformation, friction and heat has been thoroughly coated in the bath of the fluid in which is has been rolled.

As shown in FIG. 5, the upper and lower dies at the end of the stroke of the reciprocating die have not only formed the threads on the end of the rod, but due to the bath of fluid in which they have been operating, the sloping walls of the thread have been coated throughout with the zinc dust that is contained in the fluid.

The original zinc coating 9 which was on the rod end when it became subject to deformation to form the threads, has been thinned by reason of the elongation of the surface which it formerly covered. For example, as shown in FIG. 2, the dotted line R indicates the distance to which the former distance R has been deformed, and during this deformation portions of the former zinc coating have flaked off and others have been stretched and thinned so that the amount of surface coating is not sufficient to prevent rusting when put in use. As thus seen in FIG. 3, when the end of the rod has been threaded the relative surface which formerly contained a zinc coating has been practically doubled. Therefore it is necessary to recoat the threaded portions of the rod and this is accomplished by the method which I have described.

After the coating operation, I have found that it is preferable to rinse the threaded portion with hot water and then dry the same with a hot air blast. This im- 4 proves the appearance of the same and also retards the formation of zinc oxide on the surface.

From the example explained herein it can be seen that by directing a flow of fluid with zinc dust in suspension therein to the vicinity of metal deforming dies, the coating of the same can be accomplished in the same manner as described herein. Thus during metal deformation by appropriate forming dies and by providing a stream of fluid containing zinc dust at the work piece, a zinc coating can be obtained.

In butt welding tubing, which is usually done in a continuous process, a stream of fluid containing zinc dust may be directed on the finished weld as the tube is formed and suitable rollers provided for pressing a zinc coating on the weld as the tube moves forward. Since the metal at the weld is still extremely hot immediately following the formation of the weld, the zinc dust will adhere to the same and the pressure from rollers will cause a coating of zinc to form over the weld area.

I contemplate that changes and modifications may be made in the exact details shown and described and I do not wish to be limited in any particular; rather What I desire to secure and protect by Letters Patent of the United States is:

l. The method of zinc coating iron or other metal while the same is being deformed, which consists of introducing zinc dust held in suspension by a fluid to the area being frictionally heated and deformed, the zinc dust being thereby adhered or pressed on the surface of the metal at a suflicient heat to cause it to form a coating thereon, then rinsing the coated area with hot water and drying with a hot air blast.

2. The method of simultaneously threading and zinc coating a rod which consists of rolling the rod between a stationary and a movable threading die to produce heat of between and C. and introducing on the face of the die zinc dust held in suspension in a heated fluid which covers the threaded surfaces as the threads are being formed and due to the heat and friction thereby created causing the zinc dust to become malleable and ductile and be adhered to the surface of the threads to form a coating thereon.

3. The method of zinc coating iron or other metal while the same is being deformed which consists of introducing heated zinc dust held in suspension by a heated fluid to the area being frictionally heated and deformed, the zinc dust being thereby adhered or pressed on to the surface of the metal to cause it to become malleable and ductile and forming a coating thereon, then rinsing the coated area with hot water and drying with a hot air blast.

References Cited in the file of this patent UNITED STATES PATENTS 

1. THE METHOD OF ZINC COATING IRON OR OTHER METAL WHILE THE SAME IS BEING DEFORMED, WHICH CONSISTS OF INTRODUCING ZINC DUST HELD IN SUSPENSION BY A FLUID TO THE AREA BEING FRICTIONALLY HEATED AND DEFORMED, THE ZINC DUST BEING THEREBY ADHERED OR PRESSED ON THE SURFACE OF THE METAL AT A SUFFICIENT HEAT TO CAUSE IT TO FORM A COATING THEREON, THEN RINSING THE COATED AREA WITH HOT WATER AND DRYING WITH A HOT AIR BLAST. 